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Plasma IGF-I levels and cognitive performance in older women
Olivia Okereke1, Jae Hee Kang, Jing Ma
1Division of Aging, Department of Medicine, Brigham and Women's Hospital, and Harvard Medical School, 3rd floor, 181 Longwood Avenue, Boston, MA 02115, USA. ookereke@partners.org
Background:
Emerging biologic and epidemiologic evidence suggests benefits of insulin-like growth factor-I (IGF-I) in cognitive aging.
Objective:
To examine the relation of circulating IGF-I to cognition.
Methods:
We measured plasma IGF-I and IGF-binding protein-3 (IGFBP-3) in 590 women aged 60-68 years. An average 10 years later, we administered telephone-based tests of general cognition (Telephone Interview of Cognitive Status [TICS]), verbal memory, category fluency, and attention. We estimated multivariable-adjusted mean differences in performance across levels of IGF-I/IGFBP-3 molar ratio.
Results:
On the TICS, each standard deviation (S.D.) increase in molar ratio was significantly associated with better performance: multivariable-adjusted mean difference=0.2 units, 95% confidence interval (0.0,0.4), p=0.05. This effect estimate for each S.D. increase in molar ratio was cognitively equivalent to the mean difference we observed on the TICS between women 1 year apart in age. On a global score combining all tests, there was also a trend of better performance with each S.D. increase in molar ratio (p=0.07). IGF-I levels were not associated with performance in verbal memory.
Conclusions:
Higher IGF-I levels may be associated with better general cognition.
